Thermally-insulated apparatus and method of insulating the same



Apr. 24, 1923. 1 1,452,594 I G. CLAU DE THERMALLY INSULATED APPARATUS AND METHOD OF INSULATING THE SAME Filed 'Aug. .13, 1919 Z 06L syn 1111441304 Patented Apr. 24, 1923.

UNITED s r-Ar as PATENT OFFICE,

GEORGES CLAUDE, F PARIS, FRANCE, ASSIGNOR TO SOCIETE 'LAIR LIQUIDE SOCIETE ANONYME POUR LETUDE ET LEXPLOITATION DES PROCEDES GEORGES CLAUDE,

OF PARIS, FRANCE.

Tammany-INSULATED APPARATUS AND METHOD or INSULATING-THE SAME.

Application filed August 13, 19i9. Serial No. 317,322.-

To aZZ whom. it may concern:

Be it known that I, GEORGES CLAUDE, a citizen of the Republic of France, residing at Paris, France, have invented certain new.

and useful Improvements in Thermally-Insulated Apparatus and Methods of Insulating the Same (for which I have filed applications in- France on August 1 and 31, 1918); and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the artto which it appertains to make and use the same.

This invention relates to the protection of the walls of chambers wherein chemical reactions athigh pressure and temperature are conducted and has for its particular object the provision of a method and means whereby such reactions accomplished with, release '20 of heat which it is necessary to eliminate may be successfully carried out with safety,

and assurance that the desired temperatures and pressures may be successfully maintamed.

2s A further object of the invention is the provision of a method and means whereby the synthetic manufacture of ammonia, as, i described in my co-pending application Serial No. 222,502 filed March 14, 1918, may be successfully accomplished employing the very high pressures termed hyper-pressures in said application.-

Further objects and advantages of the invention will be apparent as it is better understood by reference to the following specification when read in connection with the accompanying drawing in which have illustrated in longitudinal section, one-form of apparatus adapted to the accomplishment of the desired results. In carrying out reactions at high temperature and pressure, and particularly those employed in the synthetic manufacture of ammonia, it "is of,the 'eatest importance that the wall against which the pressure is exerted should besubject only to rather low temperatures in orderthat it may preserve the requisite mechanical strength. Itis desirable, furthermore, that the 'wall be protected from the'harmful action of gases previous to orafter the reaction. These factors are an especially important desideratum in the a plication of the hyper-pressures re- ,ferre to in the" above identifie application.

' It has been previously proposed to separate the wall of the strong enclosure from the chamber wherein the reaction is conducted, and which is generally located within Other materials, the low conductivity of which is due to their porosity, such as sand, asbestos, etc., become relatively good c0nductors of heat because of the fact that the compressed gases used, particularly hydrogen, fill the voids in the materials, which thus become highly conductive of heat and particularly when the gases are employed at so-called hyper-pressures.

The principle underlying the present invention consists essentially in the use of an insulating body or substance which satisfies the demand of being wholly. or partly liquid at the high temperatures developed in the reaction chamber, which body may, however,

be solid at ordinary temperatures. It is to be noted that such a body must be neutral with reference to the materials contained within the enclosure and that its vapor tension must be low, at least at the lowest temperature obtaining inside the chamber, as will hereinafter more fully appear. This insulating liquid, forming a continuous layer between the 'wall of the enclosure and reaction chamber, protects the enclosure wall, at the same time, against unduly high temperature and contact with gases which mi ht have a deteriorating influence thereon. %y the means described, it is possible to realize mechanically, both thermic and chemical protection; a

A suitable liquid, for example, a fusible metal chloride, caustic soda or potash, may be used alone. However, in order to avoid in the liquid, movements due to convection by action of the heat, whereby the insulating be called an immobilizing agent or substance, for example, some convenient solid, preferably in pulverulent state. This body may be either porous or non-porous, provided, that it possesses poor heat conducting powers and that, of course, it is not attacked by the liquid or other materials present. By way of example, I may mention certain suitable agents which are solid at the temperature to which they are subjected. Thus sand, coke, magnesia, or magnetic oxide of iron in a very compact form resulting from the cutting of iron and steel with oxygen, may be employed. A mixture of such agents with the liquid is effected in the state of a paste or pulp, with which the space between the walls of the reaction chamber and enclosure is completely filled.

The thermal protection thus afi'orded may be supplemented by a chemical protection,

, in cases where the gases contained in the reaction chamber are soluble in the liquid employed. There is a possibility for these gases by virtue of diffusion, to slowly leak through the very hot metal wall of the reaction chamber into the liquid, or partially liquid, protective layer. These gases, should they become dissolved in the liquid, might reach the enclosing wall and should'the temperature be sufiiciently high, they might attack the metal of which the enclosing wall is constructed.

To prevent this contingency, I propose to introduce into the liquid, or partly liquid mass, one or several substances susceptible. of absorbing the gases either physically or chemically thus bringing them in a form incapable of injuring the enclosingwall. As

an example of such protection in the manufacture of synthetic ammonia I may mention the use of fused caustic soda containing a proportion of litharge (lead monoxide). The litharge converts-hydrogen into water which is retained by the soda and would, in any event, be incapable of attacking the enclosing wall. As an immobilizing agent for the liquid, coke or magnesia in'the pulverulent form could be employed.

' The insulation thus constituted affords three different kinds of protection, viz:

1. Thermally to lower the temperature of the enclosing wall. I I

2. Mechanically to prevent the gases reacting,or produced by the reaction, from di-lrectly contacting with the en losure wall and-from attack-ingjsame, and, finally,

3. Chemically by absorbing the gases reacting, or produced, which might otherwisefind their way to the enclosing wall.

It is somewhat diilicult to find bodies which will remain fusible at the rather low.

temperatures to which they are subjected in the applications intended. In conformity with the present invention, the number of uspful bodies may be increased by using cerrealized. Another plan, adapted to accomplish the same purpose, consists in using liquids which are inherently viscous. However, in view of the circumstance that it is diflicult to find a liquid which would be viscous throughout the great temperature range involved, it is desirable to use in lieu of only one liquid, a series of several viscous liquids. but of varying viscosity.-. Such liquids, if the apparatus is disposed vertically or inclined, would tend to form superposed layers conforming to their different densities. In practice it is more convenient to employ mixtures of liquids and solids as hereinbefore described.

In the accompanying drawing, I have illustrated one form f apparatus embody- .ing the .invention and adapted for the accomplishment of the desired object. It is to be understood, however, that the invention is in no way limited to the specific form of apparatus disclosed which may vary widely as to details of construction.

Referring to the drawing, the reaction re-' leasing heat which it is necessary to discharge to the exterior is carried out insidea steel tube containing in its lower part, a catalyst. The latter is surrounded by an electric heating device S serving for initiating or maintaining the reaction. The catalyzing chamber C terminates in the part B filled, for example, with asbestos, whic part B acts as a temperature exchanger. The gases necessary for the reaction enter through a lateral orifice formed at the end of the heat exchanger. Descending they pass around the heat exchanger and arrive at the end of the tube A traverse the cataparatus at ordinary temperature, the wall of the enclosure in the vicinity of the gas inlet is not subjected to a temperature sufiiciently high to'cause its deterioration either thermally or chemically. It is, therefore, unnecessary to employ theprotecting liquid at this point and the protecting liquid is em.-

. ployed',-therefore, only at the level where the .the wall.

than the other, with the protective space K filled up to the level N where under normal operating conditions the temperature is sufficiently high to maintain the protective material in a. molten state, but low enough so that the all above the point N may remain bare or unprotected without fear of chemical or thermal attacks. A very notable advantage of the particular device illustrated, considered from the standpointof the presence of vapors arising from the protective liquid which vapors may be carried over by the gases to, be combined, resides in the fact that the vapor tension to be considered is only the tension corresponding to the relatively low temperature, obtaining on the exposed or free surface of the liquid, and not the much higher vapor pressure corresponding to the 1 temperature of the liquid surrounding the reaction zone.

It should be noted, that the operation of the device, such as is illustrated, would be disturbed by the reflux .of ammonia, assuming the synthetic production of ammonia is be1ngcarried out, which may become liquefied ,at the cooler end of the interior tube B, unless the temperature is maintained above the critical temperature of ammonia, say- 130 C. In normal working, the latter result would be attained because 'of the imperfectheat, exchange between incoming and outgoing gases. During the starting period, or if found necessary during normal operation, the desired result could be realized by the aid of moderate electric heating at this end of the apparatus. v

It is furthermore t be noted'that the annular space traversed bythe gases employed in the reaction between their" inlet andtheir entrance'into the reaction chamber C should preferably be relatively narrow, or the structure should be arranged to convey the gases in the helicoidal manner in order to avoid,'by increase in velocityof the gases,

movements contrary to the direction of intended circulation, resulting from. heating the gases during their downward movement down to-A In the case where several viscous liquids are. used as abovereferred to, the least fusible liquid would, for example, cover thespace between 0' and L; the most fusible liquid which would be the least dense in the device described, would fill the space. between L and. N. Diffusion is sufficiently slow so that, in general, it would not in- "terfere with norafi'ect this mode of distribution. j Y Y Various changes may be made in carrying the invention into practice without departing therefrom or sacrificing any'of the advantages hereinbefore enumerated.

I claim:

1. The method of thermally insulating the pressure-sustaining Wall of a chamber wherein an exothermic chemical reaction at 'wherein an exothermic chemical reaction at high temperature and pressure is conducted, which comprises applying against the inner surface of the wall a neutral medium possessing a low heat conductivity and maintaining. the medium in a substantially liquid state during the reaction.

3. The method of thermally insulating the pressure-sustaining wall of a chamber wherein an exothermic chemical reaction at high temperature and pressure is conducted, which comprises applying against the inner surface of the walla medium possessing a low vapor pressure and a low heat conductivity and maintaining the medium in a substantially liquid state during the reaction. t

4. The method of thermally insulating a chamber wherein an exothermic chemical reaction at high temperature and ressure is conducted, which comprises surrounding the chamber with aeutectic mixture possessing alow heat conductivity, and maintaining the mixture in a substantially liquid state during the reaction.

5. The method, of thermally insulating a chamber wherein an exothermic chemical re-- action at high temperature and pressure is conducted, which comprises surrounding the, chamber with'a mixture of caustic soda and litharge possessing a low heat conductivity, and maintaining the mixture in a substantially liquid state'during the reaction. 6.,The method of thermally insulating a chamber wherein an exothermic chemlcal reaction at high temperature and pressure is conducted, which comprises surrounding the chamber with a succession of superposed .taining the several-media in a viscous condition during the reaction.

7. Themethod of thermally insulating a chamber Wherei'n an exother'r'nicchemical reaction athigh temperature and pressure is cond ted, which comprises surrounding the cham er With-a medium possessing a low heat conductivity and being adapted to absorb gases, and maintaining the medium in a substantially liquid state during the reaction.

8. The method of thermally insulating a chamber wherein an exothermic chemical reaction at high temperature and pressure is conducted, which comprises surrounding the chamber with a medium possessing a low \heat conductivity, maintaining the medium in a substantially liquid state during the reaction, and preventing convection currents in the liquid by the addition thereto of finely divided solid material.

9. An apparatus wherein chemical reactions at high temperature and pressure are conducted, comprising a reaction chamber, an enclosing wall spaced from said chamber and adapted to withstand internal pressure and a body within the space between said chamber and wall. said body beingsubstan tially liquid at the working temperature, neutral with reference to other materials present, and possessing a low heat conductivity and a low vapor pressure.

10. An apparatus wherein chemical reactions at high temperature and pressure are conducted, comprising a reaction chamber, an enclosing wall spaced from said chamber and adapted to withstand internal pressure and a body within the space between said chamber and wall, saidbody being substantially liquid at the working temperature, neutral with reference to other materials present, and possessing a low heat conductivity and a low vapor pressure, and having associated with it a body, which is solid at the working temperature, acting as an immobilizing agent.

11. An apparatus wherein chemical reactions at high temperature and pressure are conducted, comprising a reaction chamber, an enclosing wall spaced from said chamber and adapted to withstand internal pressure and a body within the space between said chamber and wall, said body being substantially liquid at the working temperature, neutral with reference to other materials present, and possessing a low heat conductivity and a low vapor pressure, and having associated with it a material capableof absorbing or combining-with gases introduced to or generated by the reaction.

12. An apparatus wherein chemical reactions at high temperature and pressure are conducted, comprising a reaction chamber, an enclosing wall spaced from said chamber and adapted to Withstand internal pressure and a body within the space between said chamber and wall, said body being substantially liquid at the working temperature, neutral with reference to other materials present, and possessing a low heat conductivity and a low vapor pressure, and having associated with it a body, which is solid at the working temperature, acting as an immobilizing agent and a body capable of absorbing or combinin with gases introduced to or generated by t e reaction. I

13. In an'apparatus wherein chemical reactions at high temperature and pressure are conducted, comprising a reaction chamber and enclosing wall spaced from said tem- GEORGES CLAUDE. 

